Antenna apparatus of relay system

ABSTRACT

Disclosed is an antenna apparatus of a relay system. The relay system includes a link antenna apparatus transmitting and receiving electric signals to and from a base station, a coverage antenna apparatus transmitting and receiving electric signals to and from subscriber terminals, and a repeater system connected between the link antenna apparatus and the coverage antenna apparatus to bidirectionally amplify electric signals therebetween. The antenna apparatus is one of the link antenna apparatus and the coverage antenna apparatus and includes: at least one radiation element; and a power feeder controlling electric field intensity and phases of signals transmitted from or received by the radiation element, thereby offsetting beam patterns having an influence on antenna isolation of the antenna apparatus. In the power feeder, since phase shifters and attenuators are provided at power-feed lines connected with radiation elements so as to offset the beam patterns, the link and cover-age antenna apparatuses can be disposed adjacent to each other and easily installed at reduced cost, and transmission lines can be shortened, thereby reducing the power loss.

TECHNICAL FIELD

[0001] The present invention relates to an antenna apparatus of a relaysystem, and more particularly to an antenna apparatus of a relay systemwhich can control an electric field intensity and a phase of a signalreceived by a radiation element of the antenna apparatus, therebyoffsetting a beam pattern having an influence on the antenna isolation.

BACKGROUND ART

[0002] In general, a mobile communication system, which is utilized inwireless data communications, personal communication services, wirelesslocal networks, etc., includes a base station, at least one relaysystem, and subscriber terminals; and the relay system includes a linkantenna, a repeater, and a coverage antenna.

[0003] The link antenna receives a signal from the base station andtransmits the signal to the repeater, and the repeater relays signalsbetween the link antenna and the coverage antenna. Furthermore, thecoverage antenna transmits the signal received through the link antennaand the repeater from the base station to a subscriber terminal andtransmits a signal received from a subscriber terminal to the repeater.

[0004] In the relay system operating as described above, the coverageantenna is located at an opposite position of the link antenna whilebeing spaced a predetermined distance from the link antenna, so thatsufficient antenna isolation is secured between the coverage and linkantennas, that is, the transmission and reception antennas.

[0005] In this case, the antenna isolation signifies the differencebetween intensities of a signal received by the link antenna from thebase station and a signal fed back to the link antenna after beingamplified in the repeater and then emitted through the coverage antenna.

[0006] When the difference between the intensities of the two signals issmall, the signal received by the link antenna generates oscillation ofthe repeater, and repetitive oscillation of the repeater may cause therepeater to go out of order.

[0007] Therefore, in order to prevent the repeater from oscillating, thesignal-reception level of the base station must be at least 10 dB higherthan the signal-reception level of the repeater.

[0008] Conventionally, three methods as described below are usuallyemployed in order to secure proper antenna isolation.

[0009] First, a high gain directional antenna having a highfront-to-back ratio is used.

[0010] Second, distance between the coverage antenna and a donor of therepeater is increased.

[0011] Third, antennas are shielded from each other.

[0012] In the first method, a channel selector repeater, a microwaverepeater, a laser repeater, or an optical repeater may be utilized.However, such repeaters are expensive, and it is difficult to repair andmaintain such repeaters.

[0013] In the second and third methods, a line as long as an increasedphysical distance between the antennas must be added, which therebycauses power loss between the repeater and antennas.

[0014] Further, the performance of the relay system is deteriorated,thereby reducing service coverage.

[0015] Moreover, the three conventional methods are disadvantageous inview of installation and maintenance of equipment, in that it isimpossible to employ these three conventional methods in a restrictedspace, and relatively large expense is required in employing these threeconventional methods.

DISCLOSURE OF THE INVENTION

[0016] Therefore, the present invention has been made in view of theabove-mentioned problems, and it is an object of the present inventionto provide an antenna apparatus of a relay system for a mobilecommunication service, in which phase shifters and attenuators areprovided at power-feed lines connected with radiation elements in apower feeder of the relay system, so that the power feeder can controlthe electric field intensity and phases of signals supplied to theradiation elements, thereby offsetting beam patterns having an influenceon antenna isolation of the antenna apparatus, which consequentlyenables the antenna apparatus to be easily installed at reduced cost andthe power loss to be reduced.

[0017] It is another object of the present invention to provide anantenna apparatus of a relay system for a mobile communication service,which secures necessary antenna isolation, thereby improving the qualityof the mobile communication service.

[0018] According to an aspect of the present invention, there isprovided an antenna apparatus of a relay system, the relay systemincluding a link antenna apparatus transmitting and receiving electricsignals to and from a base station, a coverage antenna apparatustransmitting and receiving electric signals to and from subscriberterminals, and a repeater system connected between the link antennaapparatus and the coverage antenna apparatus to bidirectionally amplifyelectric signals therebetween, the antenna apparatus being one of thelink antenna apparatus and the coverage antenna apparatus, the antennaapparatus comprising: at least one radiation element; and a power feedercontrolling electric field intensity and phases of signals transmittedfrom or received by the radiation element, thereby offsetting beampatterns having an influence on antenna isolation of the antennaapparatus.

[0019] Preferably, the antenna apparatus comprises: n (n is an integerlarger than or equal to one) radiation elements arranged on a flatplate, each radiation element radiating or receiving signals to betransmitted or received; a power feeder including phase shifters andattenuators provided at power-feed lines connected with the radiationelements, respectively, so that the power feeder can control theelectric field intensity and phases of the signals supplied to theradiation elements; and a coupler/distributor combining n signalsoutputted from the power feeder or distributing a signal throughmultiple paths of the power feeder.

[0020] Also, the antenna apparatus may be a passive antenna apparatuscomprising an array of at least one passive radiation element.

[0021] Otherwise, the antenna apparatus may be an active antennaapparatus comprising an array of at least one active radiation elementrequiring electric power.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The foregoing and other objects, features and advantages of thepresent invention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

[0023]FIG. 1 is a block diagram of a relay system having antennaapparatuses according to the present invention;

[0024]FIG. 2 is a view illustrating a beam pattern of antennas in aconventional mobile communication relay system; and

[0025]FIG. 3 is a view illustrating a beam pattern of antennaapparatuses in a relay system according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] Reference will now be made in detail to the preferred embodimentsof the present invention.

[0027] Referring to FIG. 1, a relay system having antenna apparatusesaccording to the present invention includes a link antenna apparatus 100transmitting and receiving electric signals to and from a base station,a coverage antenna apparatus 200 transmitting and receiving electricsignals to and from subscriber terminals, and a repeater system 300connected with and relaying electric signals between the link antennaapparatus 100 and the coverage antenna apparatus 200.

[0028] The link antenna apparatus 100 includes a radiator, a powerfeeder 150 and a coupler/distributor 140. The radiator includes n (n isan integer larger than or equal to one) radiation elements 1 ₁₁ to 1_(1n). The power feeder 150 has phase shifters and attenuators. Thecoupler/distributor 140 distributes and combines signals from the powerfeeder 150 and transmits the combined signal to the repeater system 300.

[0029] The number n of the radiation elements 1 ₁₁ to 1 _(1n) may bechanged according to intentions with which the antenna is installed.

[0030] In general, as the radiation elements 1 ₁₁ to 1 _(1n), an arrayof passive antenna radiation elements may be used. In this case, theradiation pattern of the array antenna is determined in consideration ofthe amplitude and phase of the radiation pattern of each radiationelement.

[0031] Differently from the passive array antenna, the antenna apparatusthe link antenna apparatus 100, or the coverage antenna apparatus 200may be an active antenna apparatus in which the radiation elements 1 ₁₁to 1 _(1n) themselves are provided with active devices requiringelectric power, such as low noise amplifiers and high power amplifiers,together with duplexers, thereby enabling the antenna apparatus toperform a portion of the function of the repeater system.

[0032] In the radiator, n basic radiation elements are arranged on aflat plate, and radiate or receive electric waves.

[0033] The power feeder 150 disposed at lower ends of the radiationelements 1 ₁₁ to 1 _(1n) includes phase shifters 1 ₃₁ to 1 _(3n) andattenuators 1 ₂₁ to 1 _(2n), which are connected with the radiationelements 1 ₁₁ to 1 _(1n), respectively, and control the electric fieldintensity and phase of signals supplied to the radiation elements 1 ₁₁to 1 _(1n).

[0034] The coupler/distributor 140 distributes and combines n signalsoutputted from the power feeder 150 into a single signal, and transmitsthe single signal to the repeater system 300.

[0035] Since the coverage antenna apparatus 200 has the sameconstruction as that of the link antenna apparatus 100, a detaileddescription about the construction of the coverage antenna apparatus 200will be omitted here.

[0036] The repeater system 300 is a bilateral signal amplifier employedin order to enable communication in tunnels, buildings, undergroundspaces, remote mountain places, etc., which are shadow areas forelectric wave or areas in which proper communication service cannot beprovided.

[0037] The repeater system can be realized in various forms which cansupport mobile communications by Personal Communication System (PCS),International Mobile Telecommunication (IMT) 2000, cellular phones, etc.

[0038] The repeater system 300 includes a transmission repeater section310 and a reception repeater section 320. The transmission repeatersection 310 amplifies a forward signal received through the link antennaapparatus 100 from the base station to a predetermined level and outputsthe amplified signal to the coverage antenna apparatus 200. Thereception repeater section 320 amplifies a backward signal receivedthrough the coverage antenna apparatus 200 from a terminal to apredetermined level and outputs the amplified signal.

[0039] The transmission repeater section 310 includes a first duplexer311, a low noise amplifier 312, a first attenuator 313, a first drivingamplifier 314, and a second duplexer 315. The first duplexer 311 filtersand outputs the forward signal received through the link antennaapparatus 100. The low noise amplifier 312 reduces noise of the signaloutputted from the first duplexer 311. The first attenuator 313attenuates the signal outputted from the low noise amplifier 312. Thefirst driving amplifier 314 amplifies the signal outputted from thefirst attenuator 313 to a level which enables the signal to operate aterminal. The second duplexer 315 filters the signal amplified by thefirst driving amplifier 314 and outputs the filtered signal to thecoverage antenna apparatus 200.

[0040] Correspondingly to the transmission repeater section 310, thereception repeater section 320 includes a third duplexer 321, a seconddriving amplifier 322, a second attenuator 323, a high power amplifier324, and a fourth duplexer 325. The third duplexer 321 filters andoutputs the backward signal received through the coverage antennaapparatus 200 from a terminal. The second driving amplifier 322amplifies the signal outputted from the third duplexer 321 to apredetermined level. The second attenuator 323 attenuates the signaloutputted from the second driving amplifier 322. The high poweramplifier 324 high-power amplifies the signal outputted from the secondattenuator 323. The fourth duplexer 325 filters the signal outputtedfrom the high power amplifier 324 and outputs the filtered signal to thelink antenna apparatus 100.

[0041] Since the repeater system has the same construction as that of aconventional repeater, a detailed description about the construction ofthe repeater system will be omitted here.

[0042]FIG. 3 is a view showing a beam pattern of the antenna apparatusin the relay system as described above.

[0043] Referring to FIG. 2 showing a beam pattern of the conventionalantenna, the coverage antenna and the link antenna are spaced from eachother while a natural feature or object 2 is disposed between thecoverage antenna and the link antenna, so as to prevent the beampatterns of the coverage antenna and the link antenna from having aninfluence on each other due to their side lobes.

[0044] However, as apparent from the beam patterns shown in FIG. 3, thebeam patterns of the coverage antenna and the link antenna are isolatedfrom each other even without employing a natural feature or object 2 ina relay system according to the present invention.

[0045] This is because the power feeder 150 or 250 of the antennaapparatus 100 or 200 controls the electric field intensity and phases ofthe signals transmitted from or received by the radiation elements 1 ₁₁to 1 _(1n), thereby offsetting beam patterns having an influence on theantenna isolation.

[0046] For example, directions of the beam patterns of the entire linkantenna apparatus 100 can be made different from each other by adjustingthe phase shifters 1 ₃₁ to 1 _(3n) in such a manner that the phase ofthe second radiation element 1 ₁₂ makes an angle of three degrees andthe phase of the third radiation element 1 _(1n) makes an angle of sixdegrees with reference to the first radiation element 1 ₁₁. By shiftinglocations of the side lobes through properly controlling the phaseshifters 1 ₃₁ to 1 _(3n) of the radiation elements 1 ₁₁ to 1 _(1n), thedesired beam patterns can be obtained. In this case, the sizes of theside lobes can be controlled by the attenuators 1 ₂₁ to 1 _(2n).

[0047] Reflection plates, antenna supporters, power feeder shieldingmaterials, etc. may be disposed between the link antenna apparatus 100and the coverage antenna apparatus 200, in order to increase the antennaisolation between the link antenna apparatus 100 and the coverageantenna apparatus 200.

[0048] The antenna isolation can be increased by attaching a pluralityof sheets of reflection plates to the antenna apparatus at predeterminedintervals. Further, antenna supporters made from fiberglass reinforcedplastics (FRP) instead of aluminum, which is a common material of anantenna, may be used, so as to increase the antenna isolation.

[0049] Further, power-feed lines between the antenna apparatuses and therepeater system also have an effect on the antenna isolation. In fact,each of the power-feed lines itself may function as an antenna, therebydeteriorating the antenna isolation. Therefore, in order to prevent thisdeterioration and increase the antenna isolation, a mesh grid having afunction of absorbing electric waves of the power-feed line may bedisposed between the link antenna apparatus and the coverage antennaapparatus, so as to shield the link antenna apparatus and the coverageantenna apparatus from each other.

Industrial Applicability

[0050] As can be seen from the foregoing, an antenna apparatus accordingto the present invention may be used for signals of a broad frequencyband, such as signals for mobile communications, televisionbroadcasting, FM broadcasting, etc. Especially, the antenna isolationsecured by the present invention directly relates with the quality ofservice in the field of mobile communication, so that the presentinvention enables future development and operation of communicationequipment to be carried out and communication service to be providedwith good quality and at a low price.

[0051] While this invention has been described in connection with whatis presently considered to be the most practical and preferredembodiment, it is to be understood that the invention is not limited tothe disclosed embodiment and the drawings, but, on the contrary, it isintended to cover various modifications and variations within the spiritand scope of the appended claims.

1. An antenna apparatus of a relay system, the relay system including alink antenna apparatus transmitting and receiving electric signals toand from a base station, a coverage antenna apparatus transmitting andreceiving electric signals to and from subscriber terminals, and arepeater system connected between the link antenna apparatus and thecoverage antenna apparatus to bidirectionally amplify electric signalstherebetween, the antenna apparatus being one of the link antennaapparatus and the coverage antenna apparatus, the antenna apparatuscomprising: at least one radiation element; and a power feedercontrolling electric field intensity and phases of signals transmittedfrom or received by the radiation element, thereby offsetting beampatterns having an influence on antenna isolation of the antennaapparatus.
 2. An antenna apparatus of a relay system as claimed in claim1, wherein the antenna apparatus comprises: n (n is an integer largerthan or equal to one) radiation elements arranged on a flat plate, eachradiation element radiating or receiving signals to be transmitted orreceived; a power feeder including phase shifters and attenuatorsprovided at power-feed lines connected with the radiation elements,respectively, so that the power feeder can control the electric fieldintensity and phases of the signals supplied to the radiation elements;and a coupler/distributor combining n signals outputted from the powerfeeder or distributing a signal through multiple paths of the powerfeeder.
 3. An antenna apparatus of a relay system as claimed in claim 1,wherein the antenna apparatus is a passive antenna apparatus comprisingan array of at least one passive radiation element.
 4. An antennaapparatus of a relay system as claimed in claim 1, wherein the antennaapparatus is an active antenna apparatus comprising an array of at leastone active radiation element requiring electric power.
 5. An antennaapparatus of a relay system as claimed in claim 1, wherein apredetermined object is disposed between the link antenna apparatus andthe coverage antenna apparatus, so as to increase the antenna isolationbetween the link antenna apparatus and the coverage antenna apparatus.6. An antenna apparatus of a relay system as claimed in claim 5, whereinthe predetermined object is a reflection plate, an antenna supportermade from fiberglass reinforced plastics (FRP), or a material shieldingthe power-feed lines of the power feeder.
 7. An antenna apparatus of arelay system as claimed in claim 2, wherein the antenna apparatus is apassive antenna apparatus comprising an array of at least one passiveradiation element.
 8. An antenna apparatus of a relay system as claimedin claim 2, wherein the antenna apparatus is an active antenna apparatuscomprising an array of at least one active radiation element requiringelectric power.
 9. An antenna apparatus of a relay system as claimed inclaim 2, wherein a predetermined object is disposed between the linkantenna apparatus and the coverage antenna apparatus, so as to increasethe antenna isolation between the link antenna apparatus and thecoverage antenna apparatus.
 10. An antenna apparatus of a relay systemas claimed in claim 9, wherein the predetermined object is a reflectionplate, an antenna supporter made from fiberglass reinforced plastics(FRP), or a material shielding the power-feed lines of the power feeder.